Electrical heating element for fluid media and method for producing same

Abstract

An electrical heating element for fluid media, more particularly for hot air appliances, comprising a support member of insulating material and at least two heating conductors which are made of resistance wire and which surround the support member, the heating conductors being wound as helical coils and supported on supporting edges of the support member, the coils being wound with radial spacing from one another. The heating conductors may comprise an outer coil consisting of a resistance wire of high specific power consumption and an inner coil consisting of a resistance wire of low specific power consumption. The support member may comprise a tubular body with ribs projecting radially at the periphery, said ribs forming the supporting edges. The outer ribs may be U-shaped extending from end to end of the tubular body and forming passages through which the turns of the inner coil pass. The ribs preferably comprise mica strips; various mounting means for such strips are described.

What is claimed is: 
     
       1. Electrical heating element for fluid media, especially for hot air appliances, of the type having a support member of an insulating material and at least two heating conductors of resistance wire helically wound with a mutual radial spacing therebetween and supported on supporting edges of the support member, the improvement comprising the provision of a separate and independent set of supporting edges for each of said helically wound conductors, the height and peripheral location of the supporting edges of each set being different from set to set wherein each of said resistance wires is wound around the edges of a respective one of said sets of supporting edges with the turns of the wire resting axially spaced upon the edges of the respective set, and wherein the conductors are wound with differing pitches with respect to each other in a manner so that, when viewed in a radial direction, the turns of one of the two conductors are arranged at an intersecting angle with respect to the turns of the other of the two conductors. 
     
     
       2. Heating element according to claim 1, wherein the support member comprises a tubular body with ribs projecting radially at the periphery radially outer edges of, said ribs forming the supporting edges. 
     
     
       3. Heating element according to claim 2, wherein the heating conductors comprise radially outer and inner coils, and each of the outer ribs associated with the outer coil comprise in radial planes an axially extending U-profile with U-legs directed towards the tubular body and a U-crossbar forming the supporting edge, the U-legs and U-crossbar bounding a passage for the inner coil, which is supported on inner ribs. 
     
     
       4. Heating element according to claim 3, wherein at least the outer ribs are connected to the tubular body by means of holding elements. 
     
     
       5. Heating element according to claim 4, wherein the holding elements comprise holding projections which are formed on to the tubular body at the ends and on which the ribs are secured. 
     
     
       6. Heating element according to claim 4, wherein the holding elements comprise axially disposed reception slots into which the ribs are inserted. 
     
     
       7. Heating element according to claim 2, wherein the ribs are cemented to the tubular body. 
     
     
       8. Heating element according to claim 4, wherein the ribs are cemented to the holding elements. 
     
     
       9. Heating element according to claim 8, wherein the heating conductors comprise an outer coil consisting of a resistance wire of high specific power consumption and an inner coil consisting of a resistance wire of low specific power consumption. 
     
     
       10. Heating element according to claim 9, wherein the heating conductor of the inner coil comprises a resistance wire of small cross-section which is wound about a supporting core. 
     
     
       11. Heating element according to claim 9, wherein the heating conductor of the outer coil comprises a resistance wire of rectangular cross-section and a lengthwise sinuous shape. 
     
     
       12. Heating element according to claim 9, wherein the outer coil and inner coil are wound in opposite directions so that the windings of the respective helically wound conductors are non-parallel.